Dispersion-type electroluminescent element and method for manufacturing the same

ABSTRACT

A dispersion-type EL element is a dispersion-type electroluminescent element with at least a transparent coating layer, a transparent conductive layer, a phosphor layer, a dielectric layer and a rear electrode layer sequentially formed on a base film surface. The transparent coating layer can be peeled off the surface of the base film. The transparent conductive layer is formed by applying a coating liquid composed mainly of conductive oxide particles and a binder on a surface of the transparent coating layer, applying compression processing to the applied layer and then curing the compressed layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dispersion-type electroluminescentelement obtained using a film with transparent conductive layer on whicha transparent conductive layer mainly composed of conductive oxideparticles and a binder is formed and a method for manufacturing the sameand particularly to a dispersion-type electroluminescent element appliedas a light-emitting element incorporated in a key input component ofvarious devices such as a cellular phone and the like and a method formanufacturing the same.

2. Description of the Related Art

The dispersion-type electroluminescent element (hereinafter abbreviatedas “dispersion-type EL element” in some cases) is a light-emittingelement by alternating current driving and is used for a backlight andthe like of liquid crystal display in a cellular phone, a remotecontroller and the like and an application to a light emitting elementincorporated in a key input component (key pad) of various devices hasbeen recently tried as a new usage.

Such a device includes, for example, a portable information terminal andthe like such as a cellular phone, a remote controller, a PDA (PersonalDigital Assistance), a laptop PC and the like, and the light emittingelement is used with the purpose of facilitating a key input operationin a dark place such as during a night.

ds the light emitting element of the key input component (key pad), alight emitting diode (LED) has been applied, but since there areproblems such that the LED is a point light source, its brightness on akey pad portion is non-uniform and its appearance is poor, white/blueluminescent colors are generally preferred but those colors take a highcost in the LED, power consumption is larger than the dispersion-type ELelement and the like, a trend to apply the dispersion-type EL elementinstead of the LED has become remarkable.

As a method for manufacturing such a dispersion-type EL element, thefollowing methods are widely employed in general. That is, it is amethod of sequentially forming a phosphor layer, a dielectric layer, anda rear electrode layer by screen printing and the like on a plastic film(hereinafter abbreviated as “sputtered ITO film”) on which a transparentconductive layer of an indium tin oxide (hereinafter abbreviated as“ITO”) is formed, using a physical film forming method such assputtering, ion-plating and the like.

Here, as a paste used for application (printing) formation of each layerof the phosphor layer, dielectric layer, and the rear electrode layer,phosphor particles, dielectric particles and conductive particles aredispersed, respectively, in a solvent containing a binder, and acommercial paste, for example, may be used.

The sputtered ITO film is formed so that a ITO single layer, which is aninorganic component, is formed on a transparent plastic film ofpolyethyleneterephthalate (PET), polyethylenenaphthalate (PEN) and thelike by the above physical film forming method to have a thickness ofapproximately 20 to 50 nm, and a low resistance of approximately asurface resistivity: 100 to 300Ω/□ (ohm per square) is obtained.

However, since the ITO layer is an inorganic thin film and extremelyfragile, a micro crack (split) can occur in the film, and in order toprevent that, a plastic film to be a base material needs to be providesufficient strength and rigidity and its thickness is set at least at 50μm or more, or usually 75 μm or more.

A PET film is now widely used for the base film of the above sputteredITO film, but if its thickness is less than 50 μm, flexibility of thefilm is too high and a crack can easily occur in the ITO layer duringhandling, which extremely damages conductivity of the film. Thus, a thinsputtered ITO film with the thickness of approximately 25 μm, forexample, has not been in a practical use. In the case of a soft basefilm made of urethane and the like, even if its film thickness is 75 μmor more, it can easily have a crack when the sputtered ITO layer isformed and has not been in a practical use.

Characteristics required when the dispersion-type EL element is appliedto the keypad include, as described in Patent Document 1, for example,the above-mentioned uniformity in brightness and low power consumptionand particularly, excellence in click feeling when the key pad isoperated are important.

In order not to impair the click feeling when the dispersion-type ELelement is incorporated in the key pad, the flexibility of thedispersion-type EL element itself needs to be sufficiently improved,that is, the thickness of the element is made as thin as possible or aflexible base film needs to be used.

However, if the dispersion-type EL element is manufactured using theabove-mentioned sputtered ITO film, it is necessary to have a thicknessof at least 50 μm or more for the base film in order to prevent a crackin the ITO layer so as to improve rigidity of the film, and the flexiblebase film can not be used. Thus, there is a problem that the clickfeeling of the key operation is not sufficiently favorable, if theelement is applied to the key pad.

As another problem different from the above, Patent Document 2, forexample, points out breakage/failure of an LCD (liquid crystal)component and the like caused by static electricity generated at a keyinput of a cellular phone. Thus, a similar problem might also occur in akey input component of the dispersion-type EL element, and as a measureagainst it, there is a method in which a transparent conductive layer isformed on an outer surface of the dispersion-type EL element, forexample so as to have the static electricity escape, but since the basefilm for the key pad has high flexibility as mentioned above, it can notbe applied to the conventional sputtered ITO film. Also, it is not easyto form an inexpensive transparent conductive film satisfying durability(hitting durability), transparency, conductivity required for the keypad on the outer surface of the dispersion-type EL element.

-   Patent Document 1: Japanese patent Laid-Open No. 2001-273831. with-   Patent Document 2: Japanese patent Laid-Open No. 2002-232537.

SUMMARY OF THE INVENTION

The present invention was made in view of the above conventionalcircumstances and has an object to provide a dispersion-type EL elementmore excellent in flexibility than the dispersion-type EL element usinga conventional sputtered ITO film or specifically to provide adispersion-type EL element formed on a thin or flexible transparentplastic film and a method for manufacturing the same.

In order to achieve the above object, the inventors have conductedvarious examinations and found out that in the dispersion-typeelectroluminescent elements made of at least a transparent coatinglayer, a transparent conductive layer, a phosphor layer, a dielectriclayer, and a rear electrode layer sequentially formed on a surface of abase film, the transparent coating layer is made capable of being peeledoff the base film, and by using a method of applying and forming thetransparent conducive layer on the base film not by the conventionalphysical film forming method but by using a transparent conductive layerforming coating liquid, since the transparent conductive layer is mainlycomposed of conductive oxide particles and a binder matrix, easyoccurrence of a crack in the transparent conducive layer during handlingof the transparent conductive film, which extremely impairs itsconductivity, can be suppressed, and by compression processing of theapplied layer obtained by application of the transparent conductivelayer forming coating liquid, a packing density of the conductiveparticles in the transparent conductive layer is raised, scattering oflight is lowered, and optical characteristics of the film is improved.In addition, the conductivity is drastically improved, thedispersion-type EL element more excellent in conductivity andflexibility than the dispersion-type EL element using the conventionalsputtered ITO film can be provided inexpensively, and in the case ofapplication of the dispersion-type EL element to the key pad in thecellular phone, favorable click feeling of a key operation can beobtained without any special structure or devising on the key pad, whichleads to the present invention.

That is, the dispersion-type electroluminescent element according to thepresent invention is a dispersion-type electroluminescent element madeof at least a transparent coating layer, a transparent conductive layer,a phosphor layer, a dielectric layer, and a rear electrode layersequentially formed on a base film surface, characterized in that thetransparent coating layer is formed on the base film surface using atransparent coating layer forming coating liquid mainly composed of atransparent resin and can be peeled off the base film surface, and thetransparent conductive layer is obtained by applying compressionprocessing to an applied layer formed by applying a transparentconductive layer forming coating liquid mainly composed of conductiveoxide particles and a binder on the transparent coating layer surfaceand then, curing the compressed layer.

Also, in another dispersion-type electroluminescent element according tothe present invention is characterized in that a second transparentconductive layer is further formed between the transparent base film andthe transparent coating layer, the second transparent conductive layeris formed by applying the transparent conductive layer forming coatingliquid mainly composed of the conductive oxide particles and the binderon the base film surface and curing or by applying compressionprocessing to a second applied layer formed by applying the transparentconductive layer forming coating liquid on the base film surface andthen, curing the compressed layer.

Next, another dispersion-type electroluminescent element according tothe present invention is characterized in that a thickness of thetransparent coating layer is 50 μm or less, the transparent coatinglayer is a coating layer reinforced by a fiber and/or flake particlesformed on the base film surface using an a transparent coating layerforming coating liquid mainly composed of a transparent resin and avisible-light transmissive fiber and/or flake particles, and theconductive oxide particles contain at least any one or more of indiumoxide, tin oxide, zinc oxide as main components, the conductive oxideparticle with the indium oxide as the main component is an indium tinoxide particle, the binder is cross-linkable, the transparent conductivelayer and the second transparent conductive layer have resistanceagainst organic solvent, the compression processing is conducted byrolling processing of metal rolls, the base film is peeled off andremoved at an interface with the transparent coating layer or the secondtransparent conductive layer, the above-mentioned dispersion-typeelectroluminescent element is applied as a light emitting elementincorporated in a key input component of a device, and the device is acellular phone, a remote controller, a portable information terminal.

Moreover, the method for manufacturing the dispersion-typeelectroluminescent element according to the present invention is amethod for manufacturing a dispersion-type electroluminescent element inwhich at least a transparent coating layer, a transparent conductivelayer, a phosphor layer, a dielectric layer, and a rear electrode layerare sequentially formed on a base film surface, characterized in that anapplied layer is formed using a transparent conductive layer formingcoating liquid mainly composed of the conductive oxide particles and thebinder on the transparent coating layer surface formed using an atransparent coating layer forming coating liquid mainly composed of atransparent resin and then, compression processing is conducted for thebase film on which the transparent coating layer and the applied layerare formed and then, the compressed layer is cured so as to form thetransparent conductive layer.

Next, a method for manufacturing another dispersion-typeelectroluminescent element according to the present invention is amethod for manufacturing a dispersion-type electroluminescent element inwhich at least a transparent coating layer, a transparent conductivelayer, a phosphor layer, a dielectric layer, and a rear electrode layerare sequentially formed on a base film surface, characterized in that asecond transparent conductive layer is formed by applying and curingusing a transparent conductive layer forming coating liquid mainlycomposed of the conductive oxide particles and the binder on the basefilm surface or by applying the compression processing to the secondapplied layer formed by application and then, curing the compressedlayer, the transparent coating layer is applied and formed by using thea transparent coating layer forming coating liquid mainly composed of atransparent resin on a surface of the second transparent conductivelayer and further, an applied layer is formed by using a transparentconductive layer forming coating liquid mainly composed of theconductive oxide particles and the binder on a surface of thetransparent coating layer, and then, a transparent conductive layer isformed by applying the compression processing to the base film, thesecond transparent conductive layer, the transparent coating layer, andthe applied layer and then, curing the applied layer.

Also, a method for manufacturing another dispersion-typeelectroluminescent element according to the present invention ischaracterized in that the a transparent coating layer forming coatingliquid further contains visible-light transmissive fiber and/or flakeparticles, the base film is further peeled off and removed from theinterface with the transparent coating layer or the second transparentconductive layer after the above-mentioned manufacturing process of thedispersion-type electroluminescent element, the compression processingis carried out by rolling processing of metal rolls, the rollingprocessing is carried out with a linear pressure: 29.4 to 784 N/mm (30to 800 kgf/cm), and the rolling processing is carried out with a linearpressure: 98 to 490 N/mm (100 to 500 kgf/cm).

Effect of the Invention

According to the present invention, by using a method in whichdispersion-type electroluminescent element having at least a base film,and a transparent coating layer, a transparent conductive layer, aphosphor layer, a dielectric layer, and a rear electrode layersequentially formed on the base film, in which the transparent coatinglayer can be peeled off the base film, the transparent conductive layeris applied and formed on the base film not using a conventional physicalfilm forming method but using a transparent conductive layer formingcoating liquid, since the transparent conductive layer is mainlycomposed of conductive oxide particles and a binder matrix, easyoccurrence of a crack in the transparent conductive layer duringhandling of a transparent conductive film, which remarkably impairs itsconductivity, is suppressed, and moreover, by applying compressionprocessing to an applied layer obtained by the application of thetransparent conductive layer forming coating liquid, opticalcharacteristics of a film are improved by raising a packing density ofthe conductive particles in the transparent conductive layer andlowering scattering of light and moreover, the conductivity isdrastically improved so that a dispersion-type EL element more excellentin conductivity and flexibility than the dispersion-type EL elementusing a conventional sputtered ITO film can be provided inexpensively.Also, if the above dispersion-type EL element is applied to a key pad ofa cellular phone and the like, a favorable click feeling of a keyoperation can be obtained without any special structure or devising onthe key pad, which is industrially advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating a basic structure of aconventional dispersion-type EL element.

FIG. 2 is a sectional view illustrating another structure of aconventional dispersion-type EL element.

FIG. 3 is a sectional view illustrating a dispersion-type EL elementwith a basic structure according to the present invention.

FIG. 4 is a sectional view illustrating a dispersion-type EL elementwith another structure according to the present invention.

FIG. 5 is a sectional view illustrating a dispersion-type EL elementwith still another structure according to the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

-   1 transparent plastic film-   2 transparent conductive layer-   3 phosphor layer-   4 dielectric layer-   5 rear electrode layer-   6 collecting electrode-   7 insulating protective layer-   8 base film-   9 transparent coating layer-   10 second transparent conductive layer

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The conventional dispersion-type electroluminescent element has at leasta transparent conductive layer 2, a phosphor layer 3, a dielectric layer4, and a rear electrode layer 5 sequentially formed on a transparentplastic film 1 as shown in FIG. 1, and in application to an actualdevice, as shown in FIG. 2, a collecting electrode 6 such as silver andthe like and an insulating protective layer 7 are further formed for usein general.

On the other hand, the dispersion-type electroluminescent elementaccording to the present invention has at least a transparent coatinglayer 9, the transparent conductive layer 2, the phosphor layer 3, thedielectric layer 4, and the rear electrode layer 5 sequentially formedon a base film 8 as shown in FIG. 3. In an application to an actualdevice, as shown in FIG. 4, it is used in a state where the base film ispeeled off and removed at an interface with the transparent coatinglayer (though not shown in FIG. 4, the collecting electrode such assilver and the like and the insulating protective layer are furtherformed for use in general similarly to FIG. 2).

The base film used in the present invention preferably has its thicknessof 50 μm or more.

If the thickness of the base film is less than 50 μm, rigidity of thefilm is lowered, and problems can easily occur in handling of theabove-mentioned manufacturing process of the dispersion-type EL element,curling of a base material, printability on the phosphor layer, thedielectric layer, the rear electrode layer and the like. On thecontrary, if the thickness is 150 μm or more, the base film becomes hardand difficult to be handled and is not preferable in view of cost.

Thus, considering the both, it is optimal that the thickness of the basefilm is 75 μm or more and 125 μm or less.

The base film does not require transparency but only needs to have peelproperty from the transparent coating layer, and the material is notparticularly limited but various plastics can be used. Specifically,plastics such as polycarbonate (PC), polyethersulphone (PES),polyethyleneterephthalate (PET), polyethylenenaphthalate (PEN), nylon,polyethersulphone (PES), polyimide (PI) and the like can be used. Amongthem, use of a PET film is preferable from the viewpoint of itsexcellence in price, strength, and flexibility and the like.

Here, roles of the base film include a function to ease handling of thedispersion-type EL element of the present invention in the manufacturingprocess, a function to prevent curling of the base material in alaminating process of the phosphor layer, the dielectric layer, the rearelectrode layer and the like, a function of protection duringtransportation and handling of the dispersion-type EL element, afunction to uniformly apply printing on the transparent conductivelayer, the phosphor layer, the dielectric layer, the rear electrodelayer and the like (in the screen printing in general, using a suctionstage with a large number of small-diameter holes, a pressure of thehole portion is reduced so as to fix the film, but if the film as a basematerial is thin, the film on the hole portion is deformed and holloweddue to pressure reduction, which causes a trace of this hollow on thescreen-printed film) and the like.

Since the transparent coating layer used in the present invention isapplied and formed on the base film using the transparent coating layerforming coating liquid mainly composed of a transparent resin, itsthickness can be freely set but the thickness is preferably 1 μm or moreand 50 μm or less. If the thickness of the transparent coating layerexceeds 50 μm, its rigidity is raised, and if it is incorporated in theabove-mentioned key pad as the dispersion-type EL element, a favorableclick feeling can not be obtained easily.

Also, if the thickness of the transparent coating layer is preferably 25μm or less, more preferably 15 μm or less, or further preferably 5 μm orless, a further favorable click feeling can be obtained, and since thetotal thickness of the dispersion-type EL element can be made as thin as100 μm or less, for example, it is also preferable in a point thatfreedom in designing the device is improved.

Since the transparent coating layer comes to the outermost surface ofthe dispersion-type EL element in the end, it is necessary toelectrically insulate the transparent conductive layer, but if itsthickness is less than 1 μm, there is a possibility that the insulatingcan not be sufficient, which is not favorable.

Moreover, the material of the transparent coating layer (transparentresin) is not particularly limited as long as it has peel property fromthe base film and it is possible to form the transparent conductivelayer on the layer and various resins can be used. Specifically, resinsincluding urethane, epoxy, polyester, fluorine resin and the like can beused. Among them, urethane and fluorine resins are preferable from theviewpoints of excellence in price, transparency, strength, flexibilityand the like.

Also, it is possible to reinforce the transparent coating layer with afiber and/or flake particles by having the transparent coating layerforming coating liquid further contain visible-light transmissive fiberand/or flake particles. The transparent coating layer reinforced asabove has a characteristic that the strength can be maintainedsufficiently high even if its thickness is reduced.

As the visible-light transmissive fiber (including those in a needlestate and a rod state and a whisker) used in reinforcement of thetransparent coating layer, various inorganic fibers and organic fibers(plastic fiber) can be applied as long as it is visible-lighttransmissive and a thickness of the fiber is approximately 2 to 3 μm orless. For example, the inorganic fibers include silica fiber, titaniafiber, alumina fiber, potassium titanate fiber, aluminum borate fiberand the like, and the organic fibers include polyester fiber, nylonfiber, aramid fiber and the like, but not limited to them.

As the visible-light transmissive flake particles (including those in aplate state) used for reinforcement of the transparent coating layer,various inorganic and organic (plastic) flake particles can be appliedas long as it is visible-light transmissive and a thickness of the flakeparticle is approximately 2 to 3 μm or less. For example, the inorganicflake particles include flake particles of silica, titania, alumina andthe like and a clay such as calcined kaolin and the like.

The above fibers and flake particles have an action to reinforce thetransparent coating layer in a state dispersed in a transparent resin(binder matrix), but since it is necessary to improve adhesive strengthbetween the fiber or the flake particles and the transparent resin forstrength improvement, adhesion-promoting treatment (coupling agenttreatment, plasma treatment and the like) is preferably applied on thesurface of the fiber and the flake particles as necessary. As a couplingagent in the coupling agent treatment, various coupling agents such assilane coupling agent and titanate coupling agent and the like can beapplied, for example. The silane coupling agents includeγ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane and the like, but it maybe selected as appropriate according to the type of the transparentresin in use and not limited to them.

In this way, according to the present invention, the thickness of thetransparent coating layer can be set extremely thin, and if a materialis selected as appropriate, favorable flexibility can be given accordingto usage.

In the dispersion-type EL element according to the present invention, asecond transparent conductive layer 10 may be further formed between thebase film 8 and the transparent coating layer 9 as shown in FIG. 5 (inapplication to an actual device, it is used in a state where the basefilm is peeled off and removed at the interface with the secondtransparent conductive layer 10).

The second transparent conductive layer has a purpose of preventingvarious adverse effects caused by static electricity and its resistancevalue may be much higher than the resistance value of theabove-mentioned transparent conductive layer applied as an electrode ofthe dispersion-type EL element, and the value is preferablyapproximately 1M(1×10⁶) Ω/□ or less, for example.

The second transparent conductive layer is formed by applying and curingon the base film using the transparent conductive layer forming coatingliquid in which the conductive oxide particles are dispersed in asolvent containing a binder component or by applying the transparentconductive layer forming coating liquid on the base film so as to form asecond applied layer and then, compression processing applied to thesecond applied layer and then the compressed layer is cured, but fromthe viewpoint of preventing a drop of brightness of the dispersion-typeEL element as much as possible, it preferably has a high transmittance,and thus, the film thickness is preferably 3 μm or less, or morepreferably 1 μm or less.

A material of the binder used in the second transparent conductive layeris not particularly limited as long as it has peel property from thebase film and a transparent coating layer can be formed on it, andvarious resins may be used. Specifically, resins such as urethane,epoxy, polyester, fluorine resins and the like may be used. Among them,urethane resins are preferable from the viewpoint of excellence inprice, transparency, strength and flexibility and the like.

The formation of the transparent conductive layer mainly composed of theconductive oxide particles and the binder matrix on the transparentcoating layer can be obtained by applying and drying on the surface ofthe transparent coating layer using the transparent conductive layerforming coating liquid in which the conductive oxide particles aredispersed in the solvent containing the binder component, and then, byapplying compression processing to it together with the base film onwhich the transparent coating layer is formed and then, by curing thebinder component.

The film (applied layer) before the compression processing obtained byapplying and drying the transparent conductive layer forming coatingliquid is in a state where a large number of micro voids are formedbetween the conductive particles and the binder matrix. The voids aregenerated because a mixed amount of the binder component is small in thetransparent conductive layer forming coating liquid of the presentinvention (in the case of the conductive particles/bindercomponent=90/10, for example), and close-packing of the conductiveparticles is difficult only by applying and drying the transparentconductive layer forming coating liquid, and considerable voids areformed between the conductive particles and they can not be completelyfilled by the binder component.

Here, as the compression processing, the base film having thetransparent coating layer on which the transparent conductive layerforming coating liquid is applied and dried may be rolled by steelrolls, for example. In the present invention, the dispersion-type ELelement is finally obtained with a structure having a rolling-processedtransparent conductive layer on an extremely thin transparent coatinglayer, but in the rolling processing process, since the rollingprocessing is carried out together with thick base film, a relativelyhigh rolling pressure can be applied. A linear pressure of the rollingpressure of the steel rolls in this case is preferably 29.4 to 784 N/mm(30 to 800 kgf/cm), more preferably 98 to 490 N/mm (100 to 500 kgf/cm),and further preferably 196 to 294 N/mm (200 to 300 kgf/cm). If thelinear pressure is less than 29.4 N/mm (30 kgf/cm), an effect ofimproving the resistance value of the transparent conductive layer bythe rolling processing is not sufficient, while if the linear pressureexceeds 784 N/mm (800 kgf/cm), a rolling facility would become large andthe base film and the transparent coating layer might be distorted.Considering a price of the rolling facility and a balance among thecharacteristics of the transparent conductive layer by the rollingprocessing (transmittance, haze, resistance value), the value ispreferably set as appropriate in a range of 98 to 490 N/mm (100 to 500kgf/cm).

The rolling pressure (N/mm²) in the rolling processing of the steelrolls is a value obtained by dividing a linear pressure by a nip width(width compressed by the steel rolls). The nip width is approximately0.7 to 2 mm for a diameter of approximately 150 mm, though it depends ona diameter and a linear pressure of the steel rolls.

By the rolling processing, the packing density of the conductiveparticles in the transparent conductive layer can be improved toapproximately a low value of 45 vol % or less to as high as 50 to 80 vol% (preferably 55 to 80%), for example, though it depends on the linearpressure as compared with the case without carrying out the rollingprocessing. The packing density exceeding 80 vol % seems to be difficultto be achieved, considering presence of the binder component containedin the transparent conductive layer forming coating liquid and aphysical packing structure of the conductive particles.

By carrying out such rolling processing, since the voids present in thefilm are shrunk and lost and the packing density of the conductiveparticles in the transparent conductive layer is raised, not only thatthe scattering of light is lowered and the optical characteristics ofthe film are improved but that the conductivity can be drasticallyraised.

The transparent coating layer may be applied with adhesion-promotingtreatment, or specifically, plasma treatment, corona dischargetreatment, short-wavelength ultraviolet irradiation treatment and thelike in advance in order to improve adhesion with the transparentconductive layer.

The conductive oxide particles used in the transparent conductive layerforming coating liquid are conductive oxide particles mainly composed ofany one or more of indium oxide, tin oxide and zinc oxide and include,for example, indium tin oxide (ITO) particle, indium zinc oxide (IZO)particle, indium-tungsten oxide (IWO) particle, indium-titanium oxide(ITiO) particle, indium zirconium oxide particle, tin antimony oxide(ATO) particle, fluorine tin oxide (FTO) particle, aluminum zinc oxide(AZO) particle, gallium zinc oxide (GZO) particle and the like but notlimited to them as long as transparency and conductivity are provided.

However, among them, ITO has the highest characteristics in a point thatit has both a high visible-light transmittance and an excellentconductivity and it is preferable.

An average particle size of the conductive oxide particle is preferably1 to 500 nm, and more preferably 5 to 100 nm. If the average particlesize is less than 1 nm, manufacture of the transparent conductive layerforming coating liquid is difficult and a resistance value of theobtained transparent conductive layer is high. On the other hand, if thesize exceeds 500 nm, the conductive oxide particles easily sediments inthe transparent conductive layer forming coating liquid and its handlingbecomes difficult, and simultaneous achievement of both a hightransmittance and a low resistance value in the transparent conductivelayer becomes difficult.

The size of 5 to 100 nm is more preferable because it becomes possibleto provide both the characteristics (transmittance, resistance value) ofthe transparent conductive layer and stability (sediment of theconductive particles) and the like of the transparent conductive layerforming coating liquid in a well-balanced manner.

The average particle size of the conductive oxide particles is indicatedby a value observed by a transmission electron microscope (TEM).

The binder component of the transparent conductive layer forming coatingliquid has a function to bind the conductive oxide particles togetherand to improve conductivity and strength of the film, a function toimprove adhesion between the transparent coating layer and thetransparent conductive layer, and a function to impart solventresistance in order to prevent deterioration of the transparentconductive layer caused by an organic solvent contained in variousprinting pastes used for forming of the phosphor layer, dielectriclayer, rear electrode layer and the like in a manufacturing process ofthe dispersion-type EL element. As the binder, an organic and/or aninorganic binder may be used and selected as appropriate, consideringthe transparent coating layer to which the transparent conductive layerforming coating liquid is applied and film forming conditions and thelike of the transparent conductive layer so that the above roles aresatisfied.

To the above organic binder, thermoplastic resins such as acrylic resin,polyester resin and the like may be applied, but the binder preferablyhas solvent resistance in general, and for that purpose, it should be across-linkable resin, and it can be selected from thermosetting resin,cold-setting resin, ultraviolet-curable resin, electron-beam curableresin and the like. For example, the thermosetting resins include epoxyresin, fluorine resin and the like, the cold-setting resins includetwo-component epoxy resin, urethane resin and the like, theultraviolet-curable resins include resins containing various oligomers,monomers, and photoinitiator and the like, and the electron-beam curableresins include resins containing various oligomers and monomers and thelike but not limited to these resins.

The inorganic binders include binders mainly composed of silica sol,alumina sol, zirconia sol, titania sol and the like. For example, as thesilica sol, a polymer obtained by adding water and acid catalyst totetra-alkyl silicate for hydrolysis and dehydropolycondensation is madeto progress or a polymer obtained by commercial alkyl silicate solutionwhich has been already polymerized to tetramer to pentamer is furthersubjected to hydrolysis and dehydropolycondensation and the like may beused.

If the dehydropolycondensation has progressed too much, solutionviscosity is raised and solidified in the end, and a degree ofdehydropolycondensation is adjusted to an upper limit viscosity or lessthat can be applied on a transparent substrate. However, the degree ofdehydropolycondensation is not particularly limited as long as it is alevel not more than the above upper-limit viscosity, but consideringfilm strength, weather resistance and the like, approximately 500 to50000 in a weight-average molecular weight is preferable. Then, thealkyl silicate hydrolyzed polymer (silica sol) substantially completesdehydropolycondensation reaction (cross-linking reaction) at heatingafter applying and drying of the transparent conductive layer formingcoating liquid and becomes a hard silicate binder matrix (binder matrixmainly composed of silicon oxide). The dehydropolycondensation reactionstarts immediately after drying of the film and as time elapses, thereaction solidifies the conductive oxide particles together firmlyenough to an extent that they can not move, and if the inorganic binderis used, the above-mentioned compression processing needs to beconducted as soon as possible after applying and drying of thetransparent conductive layer forming coating liquid.

As the binder, an organic-inorganic hybrid binder may be used. Forexample, such binders include a binder obtained by modifying theabove-mentioned silica sol with partially organic functional group and abinder mainly composed of various coupling agents such as a silanecoupling agent and the like.

The transparent conductive layer using the above inorganic binder or theorganic-inorganic hybrid binder inevitably has an excellent solventresistance but it should be selected as appropriate so that adhesionwith the transparent coating layer and flexibility of the transparentconductive layer and the like are not deteriorated.

A ratio between the conductive oxide particles and the binder componentin the transparent conductive layer forming coating liquid is, supposingthat specific gravities of the conductive oxide particles and the bindercomponents are approximately 7.2 (specific gravity of ITO) andapproximately 1.2 (specific gravity of usual organic resin binder),respectively, in a weight ratio, is such that the conducive oxideparticle: binder component=85:15 to 97:3, or preferably 87:13 to 95:5.The reason is that in the case of the rolling processing of the presentinvention, if the binder component is larger than 85:15, resistance ofthe transparent conductive layer becomes too high, while if the bindercomponent is smaller than 97:3 on the contrary, strength of thetransparent conductive layer is lowered and sufficient adhesion with thetransparent coating layer can not be obtained.

The transparent coating layer forming coating liquid used in the presentinvention can be obtained by dissolving the above-mentioned transparentresin (binder component of the transparent coating layer) in a solvent.

In the case of the transparent coating layer forming coating liquidcontaining fiber and/or flake particles, the liquid can be obtained bydispersing the fiber and/or flake particles, for whichadhesion-promoting treatment (coupling agent treatment, plasma treatmentand the like) is applied on the surface as necessary, in a solventcontaining a transparent resin. In this case, various coupling agentssuch as a silane coupling agent and the like, various polymer dispersingagents, various surfactants such as anionic, nonionic, cationic and thelike may be used as the dispersing agent as necessary. These dispersingagents can be selected as appropriate according to a type of the fiberand/or flake particles in use and the dispersing processing method. Asthe dispersing processing, general-purpose methods such as ultrasonicprocessing, homogenizer, paint shaker, beads mill and the like may beapplied. Concentrations of the transparent resin and the fiber and/orflake particles may be set as appropriate according to an applicationmethod in use. A mixing ratio between the transparent resin and thefiber and/or flake particles may be such that, though it depends on thematerial to be used, a mixed amount of the fiber and/or flake particlesto the total of the transparent resin and the fiber and/or flakeparticles is 5 to 60 volume %, or more preferably 10 to 30 volume %. Ifit is less than 5 volume %, the effect of reinforcement by the fiberand/or flake particles is not found, while if it exceeds 60 volume %,there are too many fiber and/or flake particles, which makes thetransparent coating layer porous and lowers the strength, and at thesame time, a surface roughness of the transparent coating layer isincreased and it becomes difficult to uniformly form the transparentconductive layer on it.

The method for manufacturing the transparent conductive layer formingcoating liquid used in the present invention will be described. First,after the conductive oxide particles are mixed with a solvent and adispersing agent as necessary, dispersing processing is applied so as toobtain a liquid with conductive oxide particles dispersed. As thedispersing agent, various coupling agents such as a silane couplingagent and the like, various polymer dispersing agents, varioussurfactants such as anionic, nonionic, cationic and the like can becited. These dispersing agents can be selected as appropriate accordingto the type of the conductive oxide particle in use and dispersingprocessing method applied. Alternatively, even if no dispersing agent isused at all, depending on a combination of the conductive oxide particleand the solvent to be applied and the dispersing method, a favorabledispersing state can be obtained in some cases. Since the use of thedispersing agent might deteriorate the resistance value of the film orweather resistance, the transparent conductive layer forming coatingliquid without using the dispersing agent is the most preferable. As thedispersing processing, general-purpose methods such as ultrasonicprocessing, homogenizer, paint shaker, beads mill and the like may beapplied.

By adding the binder component to the obtained liquid with conductiveoxide particles dispersed, and moreover, by applying componentadjustment of the conductive oxide particle concentration, solventcomposition and the like, the transparent conductive layer formingcoating liquid is obtained. Here, the binder component is added to theliquid with the conductive oxide particles dispersed, but it may beadded in advance before the dispersing process of the conductive oxideparticles and there is no particular restriction. The conductive oxideparticle concentration may be set as appropriate according to theapplication method (coating method) to be used.

A solvent used for the transparent conductive layer forming coatingliquid is not particularly limited but may be selected as appropriatedepending on the application method (coating method), film formingconditions, and a material of the transparent coating layer. Forexample, they include water, alcohol solvents such as methanol (MA),ethanol (EA), 1-propanol (NPA), isopropanol (IPA), butanol, pentanol,benzyl alcohol, diacetone alcohol (DAA) and the like, ketone solventssuch as acetone, methyl ethyl ketone (MEK), methyl propyl ketone, methylisobutyl ketone (MIBK), cyclohexanone, isophorone and the like, estersolvents such as ethyl acetate, butyl acetate, methyl lactate and thelike, glycol derivatives such as ethylene glycol monomethyl ether (MCS),ethylene glycol monomethyl ether (ECS), ethylene glycol isopropyl ether(IPC), ethylene glycol monobutyl ether (BCS), ethylene glycol monoethylether acetate, ethylene glycol monobutyl ether acetate, propylene glycolmonomethyl ether (PGM), propylene glycol ethyl ether (PE), propyleneglycol methyl ether acetate (PGM-AC), propylene glycol ethyl etheracetate (PE-AC), diethylene glycol monomethyl ether, diethylene glycolmonoethyl ether, diethylene glycol monobutyl ether, diethylene glycolmonomethyl ether acetate, diethylene glycol monoethyl ether acetate,diethylene glycol monobutyl ether acetate, diethylene glycol dimethylether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether,dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether,dipropylene glycol monobutyl ether and the like, benzene derivativessuch as toluene, xylene, mesitylene, dodecyl benzene and the like,formamide (FA), N-methyl formamide, dimethyl formamide (DMF), dimethylacetamide, dimethyl sulfoxide (DMSO), N-methyl-2-pyrolidone (NMP),γ-butyrolactone, ethylene glocol, diethylene glycol, tetrahydrofuran(THF), chloroform, mineral spirits, terpineol and the like, but notlimited to them.

Next, a method for manufacturing the dispersion-type electroluminescentelement according to the present invention will be described.

First, using the transparent coating layer forming coating liquidcontaining the resin binder (transparent resin) and the solvent, andmoreover the visible-light transmissive fiber and/or flake particles asnecessary, the transparent coating layer is formed by applying, drying,and curing it on a base film by a application method such as screenprinting, blade coating, wire-bar coating, spray coating, roll coating,gravure printing and the like. Here, prior to the formation of thetransparent coating layer, as necessary, using the transparentconductive layer forming coating liquid in which the conductive oxideparticles are dispersed in a solvent containing a binder component, asecond transparent conductive layer may be formed on the base film inadvance by applying and drying and then, curing with a method similar tothe above or curing is carried out after the compression processing tothe second applied layer formed by applying and drying. Since theresistance value of the second transparent conductive layer may be arelatively high value as mentioned above, the rolling processing doesnot necessarily have to be carried out, and in that case, though theresistance value becomes worse (or increases), the transparentconductive layer forming coating liquid with more binder components thanthe above-mentioned mixing ratio of the conductive oxide particles andthe binder component with the purpose of improving the film strength andadhesion.

Next, using the transparent conductive layer forming coating liquid, anapplied layer is formed by applying and drying on the transparentcoating layer with the method similar to the above and then, theabove-mentioned compression processing is carried out. The compressionprocessing is preferably carried out by the rolling processing of themetal rolls. After that, the rolling-processed applied layer is appliedwith curing processing such as drying curing, heat curing, ultravioletcuring and the like according to the type of the coating liquid so as tobecome a transparent conductive layer.

The term “applied layer” in the present description is used with ameaning of a film obtained by applying and drying the transparentconductive layer forming coating liquid, and the term “transparentconductive layer” is used with a meaning of a film finally obtained byusing the transparent conductive layer forming coating liquid.Therefore, the “transparent conductive layer” is used clearly separatelyfrom the “applied layer” of the transparent conductive layer formingcoating liquid.

The phosphor layer, the dielectric layer, and the rear electrode layerformed on the transparent conductive layer can be formed sequentially bythe screen printing and the like. As a paste for applying (printing) andforming each layer of the phosphor layer, the dielectric layer, and therear electrode layer, a commercially available paste can be used. Thephosphor layer paste and the dielectric layer paste are obtained bydispersing phosphor particles and dielectric particles in a solventcontaining a binder mainly composed of a fluorine rubber, respectively,and the rear electrode layer paste is obtained by dispersing conductiveparticles such as carbon particles and the like in a solvent containinga thermosetting resin binder.

Here, if each layer such as the phosphor layer and the like isscreen-printed on the transparent conductive layer, a suction stage witha large number of small-diameter holes is used in general, and a methodof fixing the film by reducing the pressure of the hole portion is used.If the base film is thin, the film on the hole portion is deformed andhollowed due to pressure reduction, which causes a problem of a trace ofthis hollow on the screen-printed film, but in the present invention, asmentioned above, a base film having a sufficient strength is used at thescreen printing, and it is peeled off and removed after thedispersion-type EL element is formed, and the problem can be prevented.

The base film used in the present invention is preferably applied withheating processing (thermal shrinkage processing) in advance at 130 to150° C., which is a thermal processing temperature of the manufacturingprocess of the dispersion-type EL element, in order to prevent shrinkage(dimensional change) by the heating processing in the manufacturingprocess of the dispersion-type EL element and curling of the film. Ifthe thermoplastic resin, thermosetting resin are used for thetransparent resin of the transparent coating layer forming coatingliquid, the heating processing (thermal shrinkage processing) can beomitted if the heating processing temperature can be set to 120 to 150°C. in the drying curing or heat curing after the transparent coatinglayer forming coating liquid is applied on the base film.

Major portions of the dispersion-type EL element are constituted by theabove transparent conductive layer, the phosphor layer, the dielectriclayer, and the rear electrode layer, but in the actual dispersion-typeEL element, a collecting electrode (formed by silver paste) of thetransparent conductive layer, a lead electrode (formed by silver paste)of the rear electrode layer, insulating protective coating (formed byinsulating paste) for preventing short-circuit between electrodes,electric shock and the like are further formed.

The dispersion-type electro luminescent element of the present inventionis excellent in flexibility as a dispersion-type EL element since thethickness of the transparent coating layer is thin and flexible, and theelement is applied as a light emitting element to be incorporated in akey input component of a device and enables obtainment of a favorableclick feeling of a key operation without any special structure ordevising of the key pad. Therefore, the element can be applied as alight emitting element to be incorporated in the key input component ofa device such as a cellular phone, a remote controller, a portableinformation terminal and the like.

EXAMPLE

Examples of the present invention will be specifically described below,but the present invention is not limited to the examples. Also, the “%”in the text indicates “weight %” except for “%” of transmittance andhaze value and a “part” indicates a “part by weight”.

Example 1

Granular ITO particles with an average particle size of 0.03 μm (productname: SUFP-HX, by Sumitomo Metal Mining Co., Ltd.) in 36 g, methylisobutyl ketone (MIBK) as a solvent in 24 g, and cyclohexanone as asolvent in 36 g are mixed and applied with dispersing processing andthen, urethane acrylate ultraviolet-curable resin binder in 3.8 g and aphotoinitiator (Darocur 1173) in 0.2 g are added and agitated well so asto obtain a transparent conductive layer forming coating liquid in whichthe ITO particles with an average dispersed particle size of 130 nm aredispersed (liquid A).

On a PET film (by Teijin Limited, thickness of 100 μm) as a base filmwithout adhesion-promoting treatment, a urethane resin solution (byAdeka Corporation, ADEKA BONTIGHTER HUX-840) as a transparent coatinglayer forming coating liquid is wire-bar coated (wire diameter: 0.4 mm)and cured at 40° C.×10 minutes −120° C.×60 minutes so as to obtain thetransparent coating layer (film thickness: 10 μm) made from a urethaneresin. On this transparent coating layer, the transparent conductivelayer forming coating liquid (liquid A) is wire-bar coated (wirediameter: 0.15 mm) and dried at 60° C. for 1 minute and then, therolling processing by hard-chromium-plated steel rolls with a diameterof 100 mm (linear pressure: 200 kgf/cm=196 N/mm, nip width: 0.9 mm) iscarried out, and the binder component is further cured (in nitrogen, 100mW/cm²×2 seconds) by a high-pressure mercury lamp so as to form thetransparent conductive layer (film thickness: 1.0 μm) constituted by theITO particles closely packed and the binder on the transparent coatinglayer and a laminate film made of base film/transparent coatinglayer/transparent conductive layer is obtained. The packing density ofthe conductive particles in the transparent conductive layer after therolling processing is approximately 57 vol %.

Since the transparent coating layer is thin as 10 μm and the urethaneresin has high transparency, visible-light absorption caused byprovision of the transparent coating layer can be ignored (transmittanceof the transparent coating layer=100%).

The film characteristics of the transparent conductive layer arevisible-light transmittance: 90.0%, haze value: 2.8%, surfaceresistivity: 645Ω/□. Since the surface resistivity is subjected toinfluence of ultraviolet irradiation at the binder curing and tends tolower temporarily immediately after the curing, measurement is made oneday after the formation of the transparent conductive layer.

The transmittance and the haze value of the above-mentioned transparentconductive layer are the values only of the transparent conductive layerand acquired by the following calculation formulas 1 and 2,respectively:Transmittance of the transparent conductive layer(%)=[(transmittancemeasured for the base film on which the transparent conductive layer andthe transparent coating layer are formed)/transmittance of the base filmon which the transparent coating layer is formed]×100  [CalculationFormula 1]Haze value of the transparent conductive layer(%)=(haze value measuredfor the base film on which the transparent conductive layer and thetransparent coating layer are formed)−(haze value of the base film onwhich the transparent coating layer is formed)  [Calculation Formula 2]

However, the transmittance and the haze value of the base film on whichthe transparent coating layer is formed are substantially equal to thetransmittance and the haze value of the base film (that is, thetransmittance of the transparent coating layer=approximately 100%, hazevalue of the transparent coating layer=approximately 0%).

The surface resistivity of the transparent conductive layer is measuredby using a surface resistivity meter Loresta-AP (MCP-T400) by MitsubishiChemical Corporation. The haze value and the visible-light transmittanceare measured by using a haze meter (HR-200) by Murakami Color Researchlaboratory Co., Ltd.

Next, on the transparent conductive layer of the laminate film, aphosphor paste (by Dupont, 7154J) in which zinc sulfide particles, whichare phosphor, are dispersed in a resin solution mainly composed offluorine polymer is made, screen printing with a size of 4×5 cm using a200-mesh polyester screen is applied, and it is dried at 120° C.×30minutes so as to form the phosphor layer.

On the above phosphor layer, a dielectric paste (by Dupont, 7153) inwhich barium titanate particles are dispersed in a resin solution mainlymade of fluorine polymer is prepared, screen printing with a size of 4×5cm using a 200-mesh polyester screen is applied, and it is dried (120°C.×30 minutes), such a screen printing step and drying step are repeatedtwice so as to form the dielectric layer.

On the dielectric layer, a carbon conductive paste (by Fujikura KaseiCo., Ltd., FEC-198) is screen-printed with a size of 3.5×4.5 cm using a200-mesh polyester screen, and it is dried at 130° C.×30 minutes so asto form a rear electrode layer.

On one ends of the transparent conductive layer and the rear electrodelayer, an Ag lead for voltage application is formed using a silverconductive paste so as to have a dispersion-type EL element according toExample 1 (base film/transparent coating layer/transparent conductivelayer/phosphor layer/dielectric layer/rear electrode layer). In order toprevent short-circuit between electrodes, electric shock and the like,as insulating protective coating of the transparent conductive layer andthe rear electrode layer, an insulating layer is formed using aninsulating paste (by Fujikura Kasei Co., Ltd., XB-101G) as necessary,but since it is not a portion relating to the essentials of the presentinvention, the details are omitted.

In the above dispersion-type EL element, the base film can be easilypeeled off at the interface with the transparent coating layer. When avoltage of 100V, 400 Hz is applied to between the leads for voltageapplication of the dispersion-type EL element obtained by peeling offthe base film, the dispersion-type EL element uniformly emits light andits brightness measurement shows 53 Cd/m². The brightness is measured bya brightness meter (by Topcon Corporation, product name: BM-9).

Example 2

In Example 1, the transparent conductive layer forming coating liquid(liquid A) is wire-bar coated (wire diameter: 0.075 mm) so as to formthe transparent conductive layer (film thickness: 0.5 μm) composed ofITO particles closely packed and the binder on the transparent coatinglayer and a laminate film constituted by base film/transparent coatinglayer/transparent conductive layer is obtained. The packing density ofthe conductive particles in the transparent conductive layer after therolling processing is approximately 57 vol %.

Similarly to Example 1 except that the transparent conductive layerhaving visible-light transmittance: 95.5%, haze value: 2.3%, surfaceresistivity: 1450Ω/□ is obtained, the dispersion-type EL elementaccording to Example 2 is obtained.

In the above dispersion-type EL element, the base film can be easilypeeled off at the interface with the transparent coating layer. When avoltage of 100V, 400 Hz is applied to between the leads for voltageapplication of the dispersion-type EL element obtained by peeling offthe base film, the dispersion-type EL element uniformly emits light andits brightness measurement shows 50 Cd/m².

Example 3

Granular ITO particles with an average particle size of 0.03 μm (productname: SUFP-HX, by Sumitomo Metal Mining Co., Ltd.) in 36 g, methylisobutyl ketone (MIBK) as a solvent in 24 g, and cyclohexanone in 36 gare mixed and applied with dispersing processing and then, urethaneacrylate ultraviolet-curable resin binder that has some adhesion but canbe peeled off a PET film in 3.8 g and a photoinitiator (Darocur 1173) in0.2 g are added and agitated well so as to obtain a transparentconductive layer forming coating liquid in which the ITO particles withan average dispersed particle size of 130 nm are dispersed (liquid B).

On a PET film (by Teijin Limited, thickness of 100 μm) as a base filmwithout adhesion-promoting treatment, the transparent conductive layerforming coating liquid (liquid B) is wire-bar coated (wire diameter:0.075 mm) and dried at 60° C. for 1 minute and then, the rollingprocessing (linear pressure: 200 kgf/cm=196 N/mm, nip width: 0.9 mm) iscarried out similarly to Example 1, and the binder component is furthercured (in nitrogen, 100 mW/cm²×2 seconds) by a high-pressure mercurylamp so as to form the second transparent conductive layer (filmthickness: 0.4 μm) constituted by the ITO particles and the binder. Thesecond transparent conductive layer has visible-light transmittance:95.0%, haze value: 2.5%, surface resistivity: 2500Ω/□. Using the sameprocedure as that of Example 1 except that the transparent coating layeris formed on the second transparent conductive layer, a transparentconductive layer (film thickness: 1.0 μm) constituted by the ITOparticles closely packed and the binder on the transparent coating layeris formed, and a laminate film constituted by base film/secondtransparent conductive layer/transparent coating layer/transparentconductive layer is obtained. The packing density of the conductiveparticles in the transparent conductive layer after the rollingprocessing is approximately 57 vol %.

Similarly to Example 1 except that the transparent conductive layerhaving visible-light transmittance: 90.2%, haze value: 2.8%, surfaceresistivity: 670Ω/□ is obtained, the dispersion-type EL elementaccording to Example 3 is obtained.

The transmittance and the haze value of the above-mentioned transparentconductive layer are the values only of the transparent conductive layerand acquired by the following calculation formulas 3 and 4,respectively:Transmittance of the transparent conductive layer(%)=[(transmittancemeasured for the base film on which the transparent conductive layer,the transparent coating layer, and the second transparent conductivelayer are formed)/transmittance of the base film on which thetransparent coating layer and the second transparent conductive layerare formed]×100  [Calculation Formula 3]Haze value of the transparent conductive layer(%)=(haze value measuredfor the base film on which the transparent conductive layer, thetransparent coating layer, and the second transparent conductive layerare formed)−(haze value of the base film on which the transparentcoating layer and the second transparent conductive layer areformed)  [Calculation Formula 4]

In the above dispersion-type EL element, the base film can be easilypeeled off at the interface with the second transparent conductivelayer. When a voltage of 100V, 400 Hz is applied to between the leadsfor voltage application of the dispersion-type EL element obtained bypeeling off the base film, the dispersion-type EL element uniformlyemits light and its brightness measurement shows 51 Cd/m².

Example 4

Urethane acrylate ultraviolet-curable resin (by Negami ChemicalIndustrial Co., Ltd., Art Resin H-14 [developed product]) as atransparent resin in 38 g and a photoinitiator (Darocur 1173) in 2 g aremixed with methyl isobutyl ketone (MIBK) in 60 g so as to obtain atransparent coating layer forming coating liquid (liquid C).

On a PET film (by Teijin Limited, thickness of 100 μm) as a base filmwithout adhesion-promoting treatment, the transparent coating layerforming coating liquid (liquid C) is wire-bar coated (wire diameter: 0.5mm) and dried at 60° C.×5 minutes and then, applied with ultravioletcuring (by a high-pressure mercury lamp, 100 mW/cm²×4 seconds) so as toobtain the transparent coating layer (film thickness: approximately 12μm) constituted by the acrylic urethane resin. The base film on whichthe transparent coating layer is formed has a transparent appearance andhas film characteristics of visible-light transmittance: 90.2% and hazevalue: 2.0% (transmittance of the transparent coatinglayer=substantially 100%).

Using the same procedure as that of Example 1 except that thetransparent conductive layer is formed on the transparent coating layer,a transparent conductive layer (film thickness: approximately 1.0 μm)constituted by the ITO particles closely packed and the binder isformed, and a laminate film constituted by base film/transparent coatinglayer/transparent conductive layer is obtained. The packing density ofthe conductive particles in the transparent conductive layer isapproximately 55 vol %.

In the above laminate film, the transparent coating layer having thetransparent conductive layer can be easily peeled off at the interfacewith the base film.

The above base film is applied with heating processing in advance at150° C.×10 minutes and then, the transparent coating layer is formed onit in order to prevent shrinkage (dimensional change) by the heatingprocessing in the manufacturing process of the dispersion-type ELelement and curling of the film.

The film characteristics of the transparent conductive layer arevisible-light transmittance: 90.5%, haze value: 2.7%, surfaceresistivity: 590Ω/□. Since the surface resistivity is subjected toinfluence of ultraviolet irradiation at the binder curing and tends tolower temporarily immediately after the curing, measurement is made oneday after the formation of the transparent conductive layer.

Using the same procedure as that of Example 1 except that the base filmon which the above transparent conductive layer is formed is used, thedispersion-type EL element according to Example 4 is obtained.

In the above dispersion-type EL element, the base film can be easilypeeled off at the interface with the transparent coating layer. When avoltage of 100V, 400 Hz is applied to between the leads for voltageapplication of the dispersion-type EL element obtained by peeling offthe base film, the dispersion-type EL element uniformly emits light andits brightness measurement shows 53 Cd/m².

Example 5

Potassium titanate fiber [K₂O 6TiO₂] surface-treated by a silanecoupling agent (γ-methacryloxypropyltrimethoxysilane) with a length of10 to 20 μm and a thickness of 0.3 to 0.6 μm (by Otsuka Chemical Co.,Ltd., TISMO N, true specific gravity=3.5 to 3.6) in 15 g and a polymerdispersing agent in 0.15 g are mixed with methyl isobutyl ketone (MIBK)as a solvent in 50 g and applied with the dispersing processing andthen, the urethane acrylate ultraviolet-curable resin (by NegamiChemical Industrial Co., Ltd., Art Resin H-14 [developed product]) in33.1 g and a photo initiator (Darocur 1173) in 1.75 g are added andagitated well so as to obtain a transparent coating layer formingcoating liquid in which the potassium titanate fibers are dispersed inthe solvent containing the transparent resin (liquid D). The mixedamount of the fibers in the transparent coating layer forming coatingliquid is, when calculated with the specific gravity of the transparentresin (including photoinitiator) supposed to be at approximately 1.2,12.6 vol %.

On a PET film (by Teijin Limited, thickness of 100 μm) as a base filmwithout adhesion-promoting treatment, the transparent coating layerforming coating liquid (liquid D) is wire-bar coated (wire diameter: 0.5mm) and dried at 60° C.×5 minutes and then, applied with ultravioletcuring (by a high-pressure mercury lamp, 100 mW/cm²×4 seconds) so as toobtain the transparent coating layer (film thickness: approximately 12μm) constituted by the acrylic urethane resin reinforced by thepotassium titanate fibers. The base film on which the transparentcoating layer is formed has a appearance of white coating film and hasfilm characteristics of visible-light transmittance: 40.8% and hazevalue: 90.8% (absorption of visible light is small but since scatteringis extremely large, apparently measured transmittance is low).

Using the same procedure as that of Example 1 except that thetransparent conductive layer is formed on the transparent coating layer,a transparent conductive layer (film thickness: approximately 1.0 μm)constituted by the ITO particles closely packed and the binder isformed, and a laminate film constituted by base film/transparent coatinglayer reinforced by fiber/transparent conductive layer is obtained. Thepacking density of the conductive particles in the transparentconductive layer after the rolling processing is approximately 55 vol %.In the above laminate film, the transparent coating layer reinforced bythe fibers having the transparent conductive layer can be easily peeledoff at the interface with the base film.

The above base film is applied with heating processing in advance at150° C.×10 minutes and then, the transparent coating layer is formed onit in order to prevent shrinkage (dimensional change) by the heatingprocessing in the manufacturing process of the dispersion-type ELelement, which will be described later, and curling of the film.

The film characteristics of the transparent conductive layer arevisible-light transmittance: 87.7%, haze value: 1.2%, surfaceresistivity: 610Ω/□. Since the surface resistivity is subjected toinfluence of ultraviolet irradiation at the binder curing and tends tolower temporarily immediately after the curing, measurement is made oneday after the formation of the transparent conductive layer.

The transmittance and the haze value of the above transparent conductivelayer are obtained by the calculation formulas 1 and 2 of Example 1, butas mentioned above, the base film on which the transparent coating layerreinforced by the fiber is formed has translucency but its transparencyis not so good with the visible-light transmittance: 40.8% and hazevalue: 90.8%. Thus, an error in a value calculated by the abovecalculation formulas might be large.

Using the same procedure as that of Example 1 except that the base filmon which the above transparent conductive layer is formed is used, thedispersion-type EL element according to Example 5 (base film/transparentcoating layer reinforced by fiber/transparent conductive layer/phosphorlayer/dielectric layer/rear electrode layer) is obtained.

In the above dispersion-type EL element, the base film can be easilypeeled off at the interface with the transparent coating layerreinforced by fiber. When a voltage of 100V, 400 Hz is applied tobetween the leads for voltage application of the dispersion-type ELelement obtained by peeling off the base film, the dispersion-type ELelement uniformly emits light and its brightness measurement shows 49Cd/m².

Example 6

On a PET film (by Teijin Limited, thickness of 100 μm) as a base filmwithout adhesion-promoting treatment, the transparent conductive layerforming coating liquid (liquid B) used in Example 3 is wire-bar coated(wire diameter: 0.075 mm) and dried at 60° C. for 1 minute and then, therolling processing (linear pressure: 200 kgf/cm=196 N/mm, nip width: 0.9mm) is carried out similarly to Example 1, and the binder component isfurther cured (in nitrogen, 100 mW/cm²×2 seconds) by a high-pressuremercury lamp so as to form the second transparent conductive layer (filmthickness: approximately 0.4 μm) constituted by the ITO particles andthe binder. The second transparent conductive layer has visible-lighttransmittance: 95.2%, haze value: 2.7%, surface resistivity: 2600Ω/□.Using the same procedure as that of Example 5 except that thetransparent coating layer is formed on the second transparent conductivelayer, a transparent conductive layer (film thickness: approximately 1.0μm) constituted by the ITO particles closely packed and the binder onthe transparent coating layer is formed, and a laminate film constitutedby base film/second transparent conductive layer/transparent coatinglayer reinforced by fiber/transparent conductive layer is obtained. Thepacking density of the conductive particles in the transparentconductive layer after the rolling processing is approximately 54 vol %.In the above laminate film, the transparent coating layer reinforced byfiber having the second transparent conductive layer and the transparentconductive layer can be easily peeled off at the interface with the basefilm and the second transparent conductive layer.

The above base film is applied with heating processing in advance at150° C.×10 minutes and then, the second transparent conductive layer isformed on it in order to prevent shrinkage (dimensional change) by theheating processing in the manufacturing process of the dispersion-typeEL element and curling of the film.

The transparent conductive layer has visible-light transmittance: 87.5%,haze value: 1.5%, surface resistivity: 620Ω/□. The conditions exceptthat the transparent conductive layer is obtained are similar to thoseof Example 1 so as to obtain the dispersion-type EL element according toExample 6.

The transmittance and the haze value of the above-mentioned transparentconductive layer are the values only of the transparent conductive layerand acquired by the calculation formulas 3 and 4 of Example 3,respectively.

In the above dispersion-type EL element, the base film can be easilypeeled off at the interface with the second transparent conductivelayer. When a voltage of 100V, 400 Hz is applied to between the leadsfor voltage application of the dispersion-type EL element obtained bypeeling off the base film, the dispersion-type EL element uniformlyemits light and its brightness measurement shows 47 Cd/m².

Comparative Example 1

In Example 1, in the process for forming the transparent conductivelayer, the transparent conductive layer (film thickness: 1.3 μm)constituted by the ITO particles not packed closely and the binder onthe PET film is formed without conducting the rolling processing (linearpressure: 200 kgf/cm=196 N/mm). The packing density of the conductiveparticles in this transparent conductive layer is approximately 44 vol%.

The film characteristics of the transparent conductive layer arevisible-light transmittance: 84.9%, haze value: 15.3%, surfaceresistivity: 21 KΩ/□. Since the surface resistivity is subjected toinfluence of ultraviolet irradiation at the binder curing and tends tolower temporarily immediately after the curing, measurement is made oneday after the formation of the transparent conductive layer.

With the process similar to Example 1 except that the base film on whichthe transparent conductive layer is formed is used, the dispersion-typeEL element according to Comparative Example 1 is obtained.

In the above dispersion-type EL element, the base film can be easilypeeled off at the interface with the transparent coating layer. When avoltage of 100V, 400 Hz is applied to between the leads for voltageapplication of the dispersion-type EL element obtained by peeling offthe base film, the dispersion-type EL element non-uniformly emits lightand has an extremely low brightness portion as approximately 30 Cd/m².

Comparative Example 2

In Example 1, using the same procedure as that of Example 1 except thatthe transparent coating layer is not formed and the PET film as a basefilm with a thickness of 100 μm applied with adhesion-promotingtreatment by corona discharge treatment is used, the transparentconductive layer (film thickness: 1.0 μm) constituted by the ITOparticles closely packed and the binder on the base film is formed. Thepacking density of the conductive particles in the transparentconductive layer after the rolling processing is approximately 60 vol %.

The transparent conductive layer has visible-light transmittance: 93.0%,haze value: 2.4%, surface resistivity: 545Ω/□. The rest is conductedsimilarly to Example 1, the dispersion-type EL element according toComparative Example 2 (PET film/transparent conductive layer/phosphorlayer/dielectric layer/rear electrode layer) is obtained.

When a voltage of 100V, 400 Hz is applied to between the leads forvoltage application of the above dispersion-type EL element, thedispersion-type EL element uniformly emits light and its brightnessmeasurement shows 53 Cd/m².

Comparative Example 3

In Comparative Example 2, similarly to Comparative Example 2 except thatinstead of the PET film having the transparent conductive layerconstituted by the ITO particles closely packed and the binder, acommercially available sputtered ITO film (visible-light transmittance:92.0%, haze value: 0%, surface resistivity: 100Ω/□) in which the ITOlayer is formed on the PET film (base film) with the thickness of 125 μmby sputtering method is used, the dispersion-type EL element accordingto Comparative Example 3 (PET film/sputtered ITO layer/phosphorlayer/dielectric layer/rear electrode layer) is obtained.

When a voltage of 100V, 400 Hz is applied to between the leads forvoltage application of the above dispersion-type EL element, thedispersion-type EL element uniformly emits light and its brightnessmeasurement shows 55 Cd/m².

The transmittance and the haze value of the above-mentioned sputteredITO film are the values only of the ITO layer and acquired,respectively, by the following calculation formulas 5 and 6:Transmittance of the ITO layer(%)=[(transmittance measured for the basefilm on which the ITO layer is formed)/transmittance of the basefilm]×100  [Calculation Formula 5]Haze value of the ITO layer(%)=(haze value measured for the base film onwhich the ITO layer is formed)−(haze value of the basefilm)  [Calculation Formula 6]

Comparative Example 4

In Example 1, the same procedure as that of Example 1 except that thetransparent coating layer is not formed and the PET film as a base filmwith a thickness of 12 μm applied with adhesion-promoting treatment bycorona discharge treatment is used, but since the thickness of the basefilm is small, wrinkles and distortion occur in the film in the rollingprocessing process, and the dispersion-type EL element can not bemanufactured.

[Strength Evaluation of Transparent Coating Layer]

The transparent coating layer (the layer obtained by peeling off andremoving the base film from the laminate film) having the transparentconductive layer obtained in each Example has a predetermined strengthsufficient for practical use. Particularly, the transparent coatinglayer reinforced by fiber having the transparent conductive layer inExamples 5 and 6 has a rupture strength of approximately twice of thatof the transparent coating layer not reinforced by the fiber having thetransparent conductive layer in Example 4, and the effect of fiberreinforcement can be confirmed (the rupture strength is measured bymaking the transparent coating layer having the transparent conductivelayer into a strip shape and conducting a tensile test on it.)

[Flexibility Evaluation of Dispersion-Type EL Element]

After the dispersion-type EL element (the element obtained by peelingoff the base film) according to each Example and the dispersion-type ELelement according to each Comparative Example are wound around a rodwith a diameter of 3 mm once each so that their light emitting faces arefaced inward and outward, respectively, a voltage of 100V, 400 Hz isapplied to between the leads for voltage application of thedispersion-type EL element and a light emitting state of the element isobserved. In each Example, no change is found in the light emittingstate. With Comparative Example 2, partially because the thickness ofthe PET film as base material is as thick as 100 μm, it is difficult towind it around the rod with the diameter of 3 mm, and when it is forced,a peeled-off portion is caused in a part of the element, which makes thelight emission non-uniform. With Comparative Example 3, a crack iscaused in the sputtered ITO layer, and almost no light is emitted fromthe element. Since Comparative Example 1 originally has non-uniformlight emission, evaluation is not made.

[Solvent Resistance Evaluation of Transparent Conductive Layer]

In each Example, after the transparent conductive layer is formed on thetransparent coating layer, the transparent conductive layer face isrubbed by a cotton swab dipped with acetone reciprocally ten times andthe change in appearance is observed, but no change is found at all. Thedispersion-type EL element is made using the evaluated transparentconductive layer and a voltage of 100V, 400 Hz is applied to between theleads for voltage application and the light emitting state of theelement is observed, but light emission is uniform, including theportion rubbed by the cotton swab, and no influence by acetone is found.

1. A method for manufacturing a dispersion-type electroluminescentelement in which at least a transparent coating layer, a transparentconductive layer, a phosphor layer, a dielectric layer, and a rearelectrode layer are sequentially formed on a base film surface,characterized in that an applied layer is formed using a transparentconductive layer forming coating liquid mainly composed of conductiveoxide particles and a binder on a surface of said transparent coatinglayer formed using a transparent coating layer forming coating liquidmainly composed of a transparent resin and then, compression processingis conducted for said base film on which the transparent coating layerand the applied layer are formed and then, the applied layer is cured soas to form the transparent conductive layer.
 2. A method formanufacturing a dispersion-type electroluminescent element in which atleast a transparent coating layer, a transparent conductive layer, aphosphor layer, a dielectric layer, and a rear electrode layer aresequentially formed on a base film surface, characterized in that asecond transparent conductive layer is formed by applying and curingusing a transparent conductive layer forming coating liquid mainlycomposed of the conductive oxide particles and the binder on said basefilm surface or by applying the compression processing to the secondapplied layer formed by application and then, curing the compressedlayer, a transparent coating layer is applied and formed by using an atransparent coating layer forming coating liquid mainly composed of atransparent resin on a surface of the second transparent conductivelayer and further, an applied layer is formed by using a transparentconductive layer forming coating liquid mainly composed of theconductive oxide particles and the binder on a surface of thetransparent coating layer, and then, a transparent conductive layer isformed by applying the compression processing to the base film, thesecond transparent conductive layer, the transparent coating layer, andthe applied layer and then, curing the applied layer.
 3. The method formanufacturing a dispersion-type electroluminescent element according toclaim 1, wherein said transparent coating layer forming coating liquidfurther contains visible-light transmissive fiber and/or flakeparticles.
 4. A method for manufacturing a dispersion-typeelectroluminescent element, characterized in that the base film isfurther peeled off and removed from an interface with said thetransparent coating layer or said second transparent conductive layerafter the manufacturing process of the dispersion-typeelectroluminescent element according to claim
 1. 5. The method formanufacturing a dispersion-type electroluminescent element according toclaim 1, wherein said compression processing is carried out by rollingprocessing of metal rolls.
 6. The method for manufacturing adispersion-type electroluminescent element according to claim 5, whereinsaid rolling processing is carried out with a linear pressure: 29.4 to784 N/mm (30 to 800 kgf/cm).
 7. The method for manufacturing adispersion-type electroluminescent element according to claim 5, whereinsaid rolling processing is carried out with a linear pressure: 98 to 490N/mm (100 to 500 kgf/cm).
 8. The method for manufacturing adispersion-type electroluminescent element according to claim 2, whereinsaid transparent coating layer forming coating liquid further containsvisible-light transmissive fiber and/or flake particles.
 9. A method formanufacturing a dispersion-type electroluminescent element,characterized in that the base film is further peeled off and removedfrom an interface with said the transparent coating layer or said secondtransparent conductive layer after the manufacturing process of thedispersion-type electroluminescent element according to claim
 2. 10. Themethod for manufacturing a dispersion-type electroluminescent elementaccording to claim 2, wherein said compression processing is carried outby rolling processing of metal rolls.
 11. The method for manufacturing adispersion-type electroluminescent element according to claim 10,wherein said rolling processing is carried out with a linear pressure:29.4 to 784 N/mm (30 to 800 kgf/cm).
 12. The method for manufacturing adispersion-type electroluminescent element according to claim 10,wherein said rolling processing is carried out with a linear pressure:98 to 490 N/mm (100 to 500 kgf/cm).